Photodegradation of azithromycin in various aqueous systems under simulated and natural solar radiation: kinetics and identification of photoproducts

This article describes the photolysis of azithromycin, a macrolide antibiotic with reported occurrence in environmental waters, under simulated solar radiation. The photodegradation followed first-order reaction kinetics in five matrices examined. In HPLC water, the degradation rate was the slowest (half-life: 20 h), whereas in artificial freshwater supplemented with nitrate (5 mg L⁻¹) or humic acids (0.5 mg L⁻¹) the degradation of azithromycin was enhanced by factors of 5 and 16, respectively, which indicated the role of indirect photolysis involving the formation of highly reactive species. Following chromatographic separation on a UPLC system, the characterization of the transformation products was accomplished using high-resolution QqToF-MS analysis. The presence of seven photoproducts was observed and their formation was postulated to originate from (bis)-N-demethylation in the desosamine sugar, O-demethylation in the cladinose sugar, combinations thereof, as well as from hydrolytic cleavages of the desosamine and/or cladinose residue. Two of these photoproducts could also be detected in natural photodegradation process in river water which was spiked with azithromycin.     

The dynamics of arsenic in four paddy fields in the Bengal delta

Irrigation with arsenic contaminated groundwater in the Bengal Delta may lead to As accumulation in the soil and rice grain. The dynamics of As concentration and speciation in paddy fields during dry season (boro) rice cultivation were investigated at 4 sites in Bangladesh and West Bengal, India. Three sites which were irrigated with high As groundwater had elevated As concentrations in the soils, showing a significant gradient from the irrigation inlet across the field. Arsenic concentration and speciation in soil pore water varied temporally and spatially; higher As concentrations were associated with an increasing percentage of arsenite, indicating a reductive mobilization. Concentrations of As in rice grain varied by 2-7 fold within individual fields and were poorly related with the soil As concentration. A field site employing alternating flooded-dry irrigation produced the lowest range of grain As concentration, suggesting a lower soil As availability caused by periodic aerobic conditions.     

Nitrogen deposition effects on Mediterranean-type ecosystems: an ecological assessment

We review the ecological consequences of N deposition on the five Mediterranean regions of the world. Seasonality of precipitation and fires regulate the N cycle in these water-limited ecosystems, where dry N deposition dominates. Nitrogen accumulation in soils and on plant surfaces results in peaks of availability with the first winter rains. Decoupling between N flushes and plant demand promotes losses via leaching and gas emissions. Differences in P availability may control the response to N inputs and susceptibility to exotic plant invasion. Invasive grasses accumulate as fuel during the dry season, altering fire regimes. California and the Mediterranean Basin are the most threatened by N deposition; however, there is limited evidence for N deposition impacts outside of California. Consequently, more research is needed to determine critical loads for each region and vegetation type based on the most sensitive elements, such as changes in lichen species composition and N cycling.     

Cocaine and other illicit drugs in airborne particulates in urban environments: a reflection of social conduct and population size

Levels of cocaine and other psychoactive substances in atmospheric particulate matter (PM) were determined in urban environments representing distinct social behaviours with regard to drug abuse: night-life, university and residential areas. Three cities (with population >1 million and <0.3 million inhabitants) were selected. Mean daily levels of drugs in PM were 11-336 pg/m³ for cocaine, 23-34 pg/m³ for cannabinoids, and 5-90 pg/m³ for heroin. The highest levels were recorded on weekends, with factors with respect to weekdays of 1-3 for cocaine, 1-2 for cannabinoids and 1.1-1.7 for heroin. Higher levels were detected in the night-life areas, pointing towards consumption and trafficking as major emission sources, and possibly ruling out drug manufacture. The similarities in temporal trends at all sites suggested a city-scale transport of psychoactive substances. Correlations were detected between cocaine and amphetamine consumption (r² = 0.98), and between heroin and cannabinoids (r²>0.82).     

Road deicing salt irreversibly disrupts osmoregulation of salamander egg clutches

It has been postulated that road deicing salts are sufficiently diluted by spring rains to ameliorate any physiological impacts to amphibians breeding in wetlands near roads. We tested this conjecture by exposing clutches of the spotted salamander (Ambystoma maculatum) to three chloride concentrations (1 mg/L, 145 mg/L, 945 mg/L) for nine days, then transferred clutches to control water for nine days, and measured change in mass at three-day intervals. We measured mass change because water uptake by clutches reduces risks to embryos associated with freezing, predation, and disease. Clutches in controls sequestered water asymptotically. Those in the moderate concentrations lost 18% mass initially and regained 14% after transfer to control water. Clutches in high concentration lost 33% mass and then lost an additional 8% after transfer. Our results suggest that spring rains do not ameliorate the effects of deicing salts in wetlands with extremely high chloride concentrations.     

Assessment of organochlorine pesticide residues in Atlantic Rain Forest fragments, Rio de Janeiro, Brazil

A superficial water quality survey in a watershed of the Paraíba do Sul River, the main water supply for the most populated cities of southeastern Brazil, was held in order to assess the impact of the expansion of agricultural activity in the near border of the Atlantic Rain Forest. The aim of this study was to investigate the presence of priority organochlorine pollutants in soils and superficial waters of Atlantic rainforest fragments in Teresópolis, Rio de Janeiro State. Soil sample preparations were compared by using ultrasound, microwave assisted extraction and Soxhlet extraction. Recoveries of matrix spiked samples ranged from 70 to 130%. Analysis of a certified soil material showed recoveries ranging from 71 to 234%. Although low concentrations of organochlorine residues were found in water and soil samples, this area is of environmental importance and concern, thus demanding a monitoring program of its compartments.     

Trees as bioindicator of heavy metal pollution in three European cities

Concentrations of four heavy metals were determined in tree leaves and bark collected from polluted and non-polluted areas of three European cities (Salzburg, Belgrade and Thessaloniki) for a comparative study. Platanus orientalis L. and Pinus nigra Arn., widespread in urban northern and southern Europe, were tested for their suitability for air quality biomonitoring. Leaves and barks were collected uniformly of an initial quantity of about 30 g of each sample. Analysis was accomplished by electrothermal atomic absorption spectrometry after total digestion. Site-dependent variations were found with the highest concentration level measured in Belgrade, followed by Thessaloniki and Salzburg. A higher accumulation of heavy metals was found in bark compared to leaves. Pine tree bark, accumulating higher concentrations of trace metals compared to plane tree bark, shows a higher efficiency as bioindicator for urban pollution. Both indicator species are suitable for comparative studies on bioindication of urban air pollution.     

Application of QuEChERS method and gas chromatography-mass spectrometry for the analysis of cypermethrin residue in milk

Analytical methods for the isolation and determination of cypermethrin in milk, based on the solid-phase microextraction (SPME) and QuEChERS methods (Quick, Easy, Cheap, Effective, Rugged, and Safe) are presented. The SPME technique was not appropriate to analyse cypermethrin in milk, even establishing the best extraction conditions, polydimethylsiloxane fiber, 60 min time extraction, 60 °C temperature extraction, addition of salt (NaCl) and stirring rate. The extraction efficiency was low probably because of the matrix constituents. The QuEChERS method involves the extraction of the analyte with acetonitrile and simultaneous liquid-liquid partitioning formed by adding anhydrous MgSO(4) plus NaCl, followed by the removal of residual water and cleanup using a procedure called dispersive solid-phase extraction, in which anhydrous MgSO(4) plus PSA and C18 are mixed with 1 mL of acetonitrile extract. The detection and quantification limits were 0.01 and 0.04 mg kg(-1), respectively, and the percentage recovery obtained ranged from 92 to 105% with relative standard deviations below 7%.     

Phytostabilization of semiarid soils residually contaminated with trace elements using by-products: sustainability and risks

We investigated the efficiency of various by-products (sugarbeet lime, biosolid compost and leonardite), based on single or repeated applications to field plots, on the establishment of a vegetation cover compatible with a stabilization strategy on a multi-element (As, Cd, Cu, Pb and Zn) contaminated soil 4-6 years after initial amendment applications. Results indicate that the need for re-treatment is amendment- and element-dependent; in some cases, a single application may reduce trace element concentrations in above-ground biomass and enhance the establishment of a healthy vegetation cover. Amendment performance as evaluated by % cover, biomass and number of colonizing taxa differs; however, changes in plant community composition are not necessarily amendment-specific. Although the translocation of trace elements to the plant biotic compartment is greater in re-vegetated areas, overall loss of trace elements due to soil erosion and plant uptake is usually smaller compared to that in bare soil.     

Functional redundancy and food web functioning in linuron-exposed ecosystems

An extensive data set describing effects of the herbicide linuron on macrophyte-dominated microcosms was analysed with a food web model to assess effects on ecosystem functioning. We showed that sensitive phytoplankton and periphyton groups in the diets of heterotrophs were gradually replaced by more tolerant phytoplankton species as linuron concentrations increased. This diet shift--showing redundancy among phytoplankton species--allowed heterotrophs to maintain their functions in the contaminated microcosms. On an ecosystem level, total gross primary production was up to hundred times lower in the treated microcosms but the uptake of dissolved organic carbon by bacteria and mixotrophs was less sensitive. Food web efficiency was not consistently lower in the treated microcosms. We conclude that linuron predominantly affected the macrophytes but did not alter the overall functioning of the surrounding planktonic food web. Therefore, a risk assessment that protects macrophyte growth also protects the functioning of macrophyte-dominated microcosms.